Old thread I know, but just got back again. Super 7's as a side-bet is not a good idea unless you count 7's backwards and divide by decks remaining. Any time this count is 5 or more: play. For 8 decks start at 32, for 6 decks start at 24. The more accurate your estimation of decks remaining, the better this works... one needs to be accurate to at least a half of a deck.
But the real edge here is to note the penetration (how far back the cut-card is). I've played the $1 bet as a nice cover when geting 6.5 or holy %$#*& 7 decks in play out of 8 !!!
Edit: mea culpa for not reading the other posts here. the old way of mine turns out to be rather accurate... 4.9/52... really? House has 11-12% advantage IIRC